Eliminate placeholder dashes on mode toggle by immediately rendering last valid data

sketch/obd2_gauge/meter.h

@@ -35,6 +35,7 @@ uint8_t pidCurrentSkip[maxpidIndex] = {}; // current skip counter
 uint8_t engine_off_count = 0; // counter to indicate engine is off then sleep
 float old_data[maxpidIndex] =
     {}; // keep old data for each gauge to improve speed for pidIndex 0-6
+float last_valid_data[maxpidIndex] = {-999, -999, -999, -999}; // keep last valid reading across view toggles
 
 // backlight variable average counter
 uint8_t low_count = 0;
@@ -371,6 +372,13 @@ int get7SegWidth(const char *str, uint8_t dW, uint8_t t) {
   return total;
 }
 
+// Forward declarations
+void plotNumeric4(uint8_t cell, float data, int warn, bool digit, String unit);
+void plotArc4(uint8_t cell, float data, int warn, int min, int max, bool digit,
+              String unit);
+void plotFullScreen(uint8_t cell, float data, int warn, int min, int max,
+                    bool digit, String unit);
+
 // 4-quadrant Numeric Meter (160x120 px)
 void numericMeter4(uint8_t cell, uint8_t pid, bool redrawHeader = true) {
   int w = 160;
@@ -392,6 +400,13 @@ void numericMeter4(uint8_t cell, uint8_t pid, bool redrawHeader = true) {
   // Clear only the body below the header to avoid any header flickering
   tft.fillRect(x + 1, y + 25, w - 2, h - 26, TFT_BLACK);
 
+  int warn = warningValue[pid].toInt();
+  bool digit = pidConfig[pid][7].toInt();
+
+  if (last_valid_data[cell] != -999) {
+    old_data[cell] = -999;
+    plotNumeric4(cell, last_valid_data[cell], warn, digit, unit);
+  } else {
     // Initial placeholder: right-aligned DSEG7 44pt number
     tft.loadFont(DSEG7_Modern_BoldItalic_44);
     tft.setTextColor(TFT_GREEN, TFT_BLACK);
@@ -399,6 +414,7 @@ void numericMeter4(uint8_t cell, uint8_t pid, bool redrawHeader = true) {
     tft.drawRightString("---", x + w - 10, y + 46, 1);
     tft.setTextPadding(0);
     tft.unloadFont();
+  }
 }
 
 void plotNumeric4(uint8_t cell, float data, int warn, bool digit, String unit) {
@@ -442,11 +458,20 @@ void arcMeter4(uint8_t cell, uint8_t pid, bool redrawHeader = true) {
   // Clear only the body below the header to avoid any header flickering
   tft.fillRect(x + 1, y + 25, w - 2, h - 26, TFT_BLACK);
 
+  int min = pidConfig[pid][4].toInt();
+  int max = pidConfig[pid][5].toInt();
+  bool digit = pidConfig[pid][7].toInt();
+  int warn = warningValue[pid].toInt();
+
   // Lowered smooth arc track (Center Y = y + 96, R = 66, IR = 54, thickness
   // 13px, sweep 130 deg: 115 to 245)
   tft.drawSmoothArc(x + 80, y + 96, 66, 54, 115, 245, TFT_DARKGREY, TFT_BLACK,
                     false);
 
+  if (last_valid_data[cell] != -999) {
+    old_data[cell] = -999;
+    plotArc4(cell, last_valid_data[cell], warn, min, max, digit, unit);
+  } else {
     // Value placeholder using DSEG7 Modern 24pt smooth font
     tft.loadFont(DSEG7_Modern_BoldItalic_24);
     tft.setTextColor(TFT_GREEN, TFT_BLACK);
@@ -454,6 +479,7 @@ void arcMeter4(uint8_t cell, uint8_t pid, bool redrawHeader = true) {
     tft.drawRightString("---", x + 116, y + 86, 1);
     tft.setTextPadding(0);
     tft.unloadFont();
+  }
 }
 
 void plotArc4(uint8_t cell, float data, int warn, int min, int max, bool digit,
@@ -508,6 +534,15 @@ void fullScreenMeter(uint8_t cell, uint8_t pid, bool redrawHeader = true) {
   // Clear only below header
   tft.fillRect(0, 38, 320, 202, TFT_BLACK);
 
+  int min = pidConfig[pid][4].toInt();
+  int max = pidConfig[pid][5].toInt();
+  bool digit = pidConfig[pid][7].toInt();
+  int warn = warningValue[pid].toInt();
+
+  if (last_valid_data[cell] != -999) {
+    old_data[cell] = -999;
+    plotFullScreen(cell, last_valid_data[cell], warn, min, max, digit, unit);
+  } else {
     if (!cellIsNumeric[cell]) {
       // Arc mode full screen
       // Large full screen arc (Center: 160, 195, R: 130, IR: 108, thickness 23px,
@@ -530,6 +565,7 @@ void fullScreenMeter(uint8_t cell, uint8_t pid, bool redrawHeader = true) {
       tft.setTextPadding(0);
       tft.unloadFont();
     }
+  }
 }
 
 void plotFullScreen(uint8_t cell, float data, int warn, int min, int max,
@@ -736,6 +772,8 @@ void updateMeter(uint8_t pidNo, String response) { // update parameter on screen
   }
   }
 
+  last_valid_data[pidNo] = data;
+
   // Engine off check if PCM volt or ATRV
   if (pidConfig[pidIdx][2] == "0142" || pidConfig[pidIdx][2] == "ATRV") {
     engine_onoff(data, pidNo);

sketch/obd2_gauge/obd2_gauge.ino

@@ -498,7 +498,6 @@ void loop() {
       // In full screen: single click toggles between arc and number mode without header flicker
       cellIsNumeric[fullScreenCell] = !cellIsNumeric[fullScreenCell];
       fullScreenMeter(fullScreenCell, pidInCell[fullScreenCell], false);
-      old_data[fullScreenCell] = -999;
     } else if (clickQuadrant >= 0 && clickQuadrant < 4) {
       // In 4 quadrants: single click toggles between arc and number for this quadrant without header flicker
       cellIsNumeric[clickQuadrant] = !cellIsNumeric[clickQuadrant];
@@ -508,7 +507,6 @@ void loop() {
       } else {
         arcMeter4(clickQuadrant, pid, false);
       }
-      old_data[clickQuadrant] = -999;
     }
   }
      //----------------------